Wireless and mobile network operators face the continuing challenge of building networks that effectively manage high data-traffic growth rates. Wireless and mobile technology standards are evolving towards higher bandwidth requirements for both peak rates and cell throughput growth.
Conventional radio base stations employed in wireless networks which utilize various 2G, 3G and 4G radio technologies (such as CDMA, 1XEV-DO, WCDMA, WiMAX-SISO, LTE-SISO, etc.) routinely include an Uplink Diversity feature. Wireless base stations have been equipped for Uplink Diversity for more than 20 years.
When a base station includes this feature, the system performance may be enhanced by employing two diversity antennas for the uplink receive function. Two receive antennas when deployed in conjunction with a suitable signal combining means in the base station can help mitigate multipath radio propagation effects. The performance enhancement obtained with two receive antennas (compared to the system performance with only one uplink receive antenna) can range from 3 to 10 dB or more (when applied to the system link budget) under various propagation conditions and for various antenna types. The impacts of uplink diversity may also include reducing the mobile transmit power and thereby increasing the mobile's battery service period as well as helping reduce intra-system and inter-system interference. The base station's uplink diversity feature employing diversity antennas can be quite advantageous, therefore most wireless network operators require 2G, 3G and 4G base stations they purchase and deploy to have an uplink diversity capability. Base stations equipped for uplink diversity have two separate receive antenna ports.
Some base stations combine the transmit and receive functions for one of the antenna ports by providing the downlink transmit function and main uplink receive antenna function on the same antenna port. The second antenna port is assigned to the diversity receive antenna. Such base stations have a total of two antenna ports per sector.
FIG. 1 shows two example architectures of a conventional DAS deployment, one where the remote antenna units are configured for non-diversity and a second one where the remote antenna units are configured for a diversity implementation. The host unit is connected to the remote antenna unit by optical fiber. For the diversity implementation, two separate uplink inputs are shown at the remote antenna unit and two uplink ports are shown at the base station. For the non-diversity implementation, only one uplink input is shown at the remote antenna unit and one uplink port is shown at the base station. Despite the progress made in communications systems, there is a need in the art for improved methods and systems related to communications technology.